Activation of catalysts



Aug. l5, 1944.

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ACTIVATION OF CATALYSTS Filed Oct. 23, 1941 QNNNNOWWQ d @xml Bk. c

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hm mm VPatented Aug. 15, 1944 V UNITED ACTIVATION F CATALYSTS VanderveerVoorhees, Homewood, Ill., asslgnor to Standard Oil Company, Chicago,Ill., a corporation of Indiana Application October 23, 1941, Serial No.416,246

' (ci. 19e- 52) Claims.

This invention relates to the catalytic conversion of hydrocarbons andmore particularly to the conversion of naphthas of low knock rating intohigh knock rating gasoline. It relates to conversion of hydrocarbons bycontacting with porous solid catalysts at high conversion temperaturesand more specically, the invention relates to the catalytic conversionof hydrocarbon oils in the vapor phase in contact with solid catalystscontaining as promoters certain metal oxides having a tendency tosublime.

One object of the invention is to improve the conversion Iofhydrocarbons in contact with catalytic oxides which normally suiferlosses by sublimation. Another object of the invention is to provide aconvenient and economical method of applying promoters to hydrocarbonconversion catalysts and particularly reforming catalysts.

The invention is illustrated by a drawing which shows diagrammaticallyan apparatus for carrying out the process.

It has been found that in the reforming and 'hydroforming of heavynaphthas when employing an oxide of molybdenum or chromium the activityof the catalyst diminishes progressively to a point where conversionofthe hydrocarbon becomes significantly lower as the age of the catalystincreases. It is necessary to discard the catalyst and replace it withfresh catalyst. In the case of an aluminum oxide catalyst promoted with8.7% of molybdenum, for example, the` molybdenum content of the catalystdiminished to '7.5% in a relatively short time of operation.Investigation showed that this Was apparently due to sublimation of themolybdenum oxide from of the oxides of the metals of the left column ofgroups V and VI of the periodic system which have the property ofsubliming, especially in their higher states of oxidation. The amount ofthe promoter oxide present on the alumina will usually be in theapproximate range of 5 to 25%, 10% being commonly employed. Althoughalumina is the preferred support for this catalyst,

certain other oxides may be employed, particularly the oxides ofmagnesium, titanium and thorium.

In preparing these catalysts with sublimable oxides, the promoter metaloxides or hydroxides may be co-precipitated with the catalyst body fromaqueous solutions, for example, -by adding ammonia to the desired metalsalts, followed by washing, drying and igniting the product. Thus, asolution of molybdenum sulfate and aluminum sulfate may be precipitatedwith ammonia. When using the chlorides, it is not necessary to wash outthe ammonium chloride which is volatile and this `is also true of othersalts which are easily volatilized.

Another method of preparing the catalyst is to deposit the promoter onthe support, for example, active alumina, bauxite, alumina gel, etc.,either by precipitation or by impregnationwith a solution of thenitrate, for example, or an ammonium salt of the promoter metal oxygenacid. Thus, molybdenum nitrate or ammonium molybdate may be impregnatedinto activated alumina and then dried and ignited to convert themolybdenum to the oxide.

According to my invention, I may also introduce the promoter metal oxideinto the alumina or other supporting material by subliming at elevatedtemperature in a current of hot 'gas and passing the stream of gasbearing the metal oxide vapor through the alumina support suitablycontained in a granular bed. The volatile metal oxide is adsorbed fromthe gas into the pores and on the surface of the active alumina or othersupporting material, thereby effecting the desired activation. However,my invention relates primarily to preventing Vdeterioration or restoringthe activity of the catalyst which has suffered deterioration in use. Myinvention will be more readily understood by referring to theaccompanying drawing, which is a simplified iiow diagram omittingvarious detailed equipment, the use of which will be apparent to thoseskilled in the art.

In the drawing, furnace i, which may be suitably a conventional pipefurnace, is employed to heat the hydrocarbon feed stock. Reactionchambers 2 and 3 contain the conversion catalyst and are usedalternately, the catalyst being regenerated in one While the other is inoperation. Heater 4 is provided to supply heat to the regenerationgases. Its use is optional. Sublimator drum 5 contains the metal oxidepromoter I to besublimed into the catalyst during regeneration.Fractionator 6 effects an initial separation i hydrocarbon vapors passesdown tivity. While the catalyst ot the products of the reaction. Atypical'operation oi' the process is as follows: A mid-continent virginheavy naphtha having an octane number of about 40 A. B. T. M. and aboiling range ol' about 325 to 450 F. is charged to the system by line land pump il. In furnace I it isvaporized and heated to the desiredconversionjtemperature or'somewhat above and the vapors are conducted byline I2 to reactor 2. About 3 mois of hydrogen per mol of feed areintroduced by pump I3 and line I4, passing through the heater with thefeed stock. The mixture of hydrogen and through reactor 2 in contactwith the granular catalyst therein which may be granules of activealumina promoted with 8 to 10% of chromium oxide or molybdenum oxide ora mixture of the two. Granules employed for this purpose mayconveniently have a particle size oi V4 to ovmesh, fine material beingavoided to prevent plugging and excessive pressure drop in passingthrough the reactor. Space velocities (V. H. VJ may be about 1,4; to 5volumes of liquid feed per hour per apparent volume of catalyst. A spacevelocity of 1 to 2 volumes per hour per volume of catalyst is typical. Atemperature of 925 to 975 F. and a pressure of about 200 to 400 poundsper square inchmay be employed.

The hydrocarbon vapors and e.hydrogen pass out of the bottom of thereactor through a suitable, perforated supporting diaphragm and areconducted by line illi to Iractionator 6 where heavy constituents arecondensed and separated from gasoline and lighter products. The gasolineis condensed in condenser it and? collected in receiver l1 whence it isivithdraw'n by line i8. Uncondensed gases are withdrawn by line I8 but alarge part of the uncondensed gases may be recycled by line and blower2i to the conversion system. The hydrogen contained in these gases mayamount to to 75 Volume per= cent and it supplements or may convenientlyreplace the hydrogen introduced at it, a larger amount of the gasesbeing employed in the latter case to maintain the desired hydrogen tohydrocarbon ratio. After the catalyst in reactor 2 has suered rdient. Itfurther appears that a substantial loss of activity. primarily from thedeposition of carbonaceous matter thereon, the now of vapors through itis interrupted by clos. ing valves 22 and 23 and opening valves 2li and'25, thereby diverting the stream through reactor 3 in which thecatalyst has been restored to acin reactor 2 is still hot regenerationis begun by introducing heated regeneration gas by line 26. The hotregeneration gas containing oxygen passes through a bed of catalyst inreactor 2 and is conducted away by line 2l. A portion of theregeneration gas may be conducted by valved lixie 28 to sublimingchamber 5 where it collects volatile metal oxides and conducts themthrough line 29 to reactor 2 in contact with the catalyst there. Duringthe regeneration of the catalyst the temperature may be of the order of1000 to 1400 F. or even higher, e. g., 1600 F. A temperatureof -1100 to1200 F. is generally not exceeded since an excessively high temperatureduring regeneration of the catalyst impairs its activity more or lesspermanently.

When employing a molybdenum oxide proj moted catalyst in reactor 2, Imay employ molybdenum trioxide in sublimation chamber 5 and I may'heatlthe chamber 5 externally to a tem perature of about 1100 to 1500* F. orhigher to sublime a portion of the molybdenum oxide and disperse it inthe vapors passing out through 2l into reactor 2. In reactor 2 themolybdenum oxide vapors introduced during regeneration and preferablyduring the entire period ot regeneration, are deposited on the catalysttherein and prevent a net loss oLmoiybdenum oxide by sublimation.Otherwise. loss of molybdenum oxide occurs during each regenerationperiod of the cycle lmpoverishing the catalyst oi this ingremolybdenumoxfde lost from the catalyst by sublimation is logt principally from theactive centers of the catalyst and the resulting 4loss oi catalystemciency is greater than would be' expected from the amount of promoterremoved. It is an ob. .lect of this invention to maintain ln theregeneration gases sumcient promoter oxide vapors for saturation,thereby preventing sublimation oi the promoter oxide from active centersof tho catalyst.

A stream of oxygen-containing regeneration gases entering the top of thereactor 2 by lines 28 and 3d passes downward through the catalyst andeilects removal oi carbon therefrom by com. bustion, care being taken toavoid local overheating above the desired regeneration temperature, forexample, 1100 F. Spent regeneration gases depart by line 3| connectingwith mani.. fold 2l and ow thence through exchanger I2 to discharge line$3. Air supplying oxygen for regeneration may be admitted by line @t andheated in exchanger 32, thence conducted by line 35 to blower 3e whichforces it through the furnace d as hereinabove mentioned. Spent re.generation gases may be recycled through valved line el to control theamount of oxygen in the fresh regeneration gas as desired.

It is not always necessary to heat the regeneration gas and in factheater may be substid tuted or supplemented by a cooler or theregeneration gases may by-pass the heater by line 33. In fact, thenecessity of dissipating heat `from the catalyst during regenerationencourages supplying cool regeneration gases after the regenerationreaction has been inaugurated. When regenerating with cool gases, forexample. gases having a temperature below 900 F., itis advisable toraise the temperature of the regeneration gases at the end oi theregeneration step to 1000 F. or 1100 them saturated with promoter oxideat that temperature. In that Way an additional supply of the promoteroxide is furnished to the catalyst to offset any depletion which hasoccurred.

When the catalyst in reactor 2 has been regenerated and theicatalyst inreactor 3 has be' come deactivated, the operations of conversion andregeneration may be reversed, reactor 2 being employed for conversion ofhydrocarbons as previously described and the catalyst in reactor 3 beingregenerated in the same manner as just described for reactor 2. Morereactors may be employed in the system and regenerated in rotation. o

Instead of introducing the subllmable metal oxide promoter by means ci'a subliming chamber as above described, I of the promoter oxide lyst bedin the reactor section of reactor 2 wherein a layer of granularmolybdenum oxide is indicated at 39. A layer of catalyst may be placedabove the layer of promoter oxide if desired to insure that the oxide beeilectively heated to subliming temperature to the surface of the cata-F., thereabout, and have may simply apply a layer` as shown in thecut-away by the combustion of carbonaceous deposits on the catalystduring regeneration. Likewise, layers of promoter oxide may bealternated with catalyst layers throughout the catalyst bed if desired.I also contemplate conducting the ilow of gases upwardly through thereactor in which case I may introduce the sublimable metal oxidepromoter at the bottom of the reactor. I also contemplate introducingthe promoter metal oxide periodically during the operation of theprocess rather than continuously with each regeneration.

Having thus described my invention what I claim is:

1. Inv theprocess of converting hydrocarbons by contacting at a highconversion temperature with a solid conversion catalyst containing as anessential ingredient a sublimable metal oxide which is unavoidably lostfrom the catalyst by sublimation, the improvement comprisingperiodically restoring the sublimable metal oxide to the catalyst bypassing through said catalyst, gas, at a high temperature, containingvapors of said metal oxide.

2. The process of claim 1 wherein said sublimable metal oxide` is anoxide of chromium.

3. The process of claim 1 wherein said sublimable metal oxide is anoxide of molybdenum.

4. In the process of converting hydrocarbon oils wherein the vapors ofan oil are subjected at conversion temperature to the action of a solidmetal oxide catalyst containing as an essential ingredient a sublimablemetal oxide promoter and wherein said catalyst' is periodicallyregenerated by combustion with an oxidizing regeneration gas at anelevated temperature to remove carbonaceous deposits and said promoteroxide is unavoidably lost from said; catalyst by sublimation during saidregeneration, the improvement comprising saturating said regenerationgas with the vapors of said promoter oxide while introducing it intosaid catalyst, thereby retarding the vaporization of the promoter fromsaid catalyst.

5. The process of claim 4 wherein said catalyst `is alumina promotedwith chromium oxide.

8. The process of claim 4 wherein said catalyst consists essentially ofactive aluminum oxide and an amount of said sublimable metal oxidepromoter within the approximate range of 5 to 25%.

9. The process of reforming low knock rating heavy .naphtha whichcomprises vaporizing the naphtha and subjecting the vapors in thepresence of hydrogen to the action of a catalyst consisting essentiallyof active aluminum oxide and a sublimable metal oxide promoter,maintaining a reaction temperature of about between 850 and 1050 F.,maintaining a pressure of about between 50 and 400 pounds per squareinch and a space velocity of about 1 to 2 V. H. V., continuing thepassage of naphtha vapors and hydrogen through said catalyst until itsactivity is substantially -impaired, interrupting the iiow of naphthavapors and regenerating said catalyst by passing an oxygen-containingregeneration gas therethrough, maintaining the temperature of saidcatalyst during regeneration at a point between about 1000 and 1200 F.,continuing the regeneration until carbonaceous deposits are substantially removed from said catalyst by combustion and substantiallypreventing the loss oi the sublimable metal oxide promoter from saidcatalyst by dispersing in said regeneration gases before contacting withsaid catalyst additional amounts gf said sublimable metal oxide promoterin vapor orm.

10. The process oi claim 9 wherein said promoter is an oxide ofmolybdenum.

VANDERVEER VOORHEES.

